1. Field of the Invention
The present invention relates to a reverse charging system, a reverse-charging service control apparatus, a call agent and a reverse charging method. More particularly, it relates to a reverse charging system, a reverse-charging service control apparatus, a call agent and a reverse charging method for providing a reverse charging service in a telephone network which is capable of interconnecting IP telephone sets and public switching telephone sets.
2. Description of the Related Art
In the existing PSTN (Public Switching Telephone Network), exchanges operate in concert with IN (Intelligent Network) apparatuses through a common channel signaling system, whereby telephone services of high functions are provided.
One of the telephone services is a reverse charging service which is currently rendered in the PSTN, and which uses special numbers beginning with a number “0120”. The reverse charging service in the PSTN is stated in, for example, JP-A-2001-309088. In an invention stated in this document, telephone numbers for reverse charging and the called destination telephone numbers of service contractors are registered in a database for providing the reverse charging service. In a case where a call to any service contractor has originated, an exchange which accommodates a call originating terminal identifies the called destination telephone number to be a subject for the reverse charging service, and it notifies the reverse-charging telephone number to a network service control station which is a kind of IN apparatus. The network service control station searches the database for the called destination telephone number corresponding to the reverse-charging telephone number, it notifies the sought destination telephone number to the originating exchange, and it performs a calling connection process for the destination telephone number. At the same time, the network service control station instructs the originating exchange not to charge a call fee to the call originator. When telephonic communication has ended, the network service control station generates fee information in which the called destination telephone number is set as the charged party of a call fee, and it transmits the information to a billing center.
The reverse charging service is provided in the PSTN by the method as stated above. In recent telephone networks, the PSTN and IP (Internet Protocol) networks are being merged. It is desired to render the various telephone services having been provided in the PSTN, also for IP telephone sets.
Besides, in general, in the connection between the PSTN and the IP network, the interconnection is realized by installing a media gateway (MG) which cross-converts the STM (Synchronous Transfer Mode) voice signal data of the PSTN and IP voice packets, a signaling gateway (SG) which connects a common channel signaling network and the IP network so as to transmit and receive control signals, and a call agent (CA) which converts a common channel signal received by the SG, into a signal for an MG control conforming to an MGCP (Media Gateway Control Protocol), so as to perform the MG control. These techniques are stated in, for example, “Nikkei Communications”, Issue of Aug. 7, 2000, p. 104-p. 105.
This connection system will be outlined. First, in a case where an IP telephone subscriber has originated a call from an IP telephone to a PSTN subscriber telephone, the CA receives the calling source telephone number of the IP telephone being a call originator, and a called destination telephone number. Subsequently, the CA searches a database for the IP address of the MG connected with an exchange which accommodates the PSTN subscriber telephone being a called destination, on the basis of the toll number of the received called-destination telephone number, and it is connected with the MG. Further, the CA is connected with the exchange on the basis of the called destination telephone number so as to permit telephonic communication with the PSTN subscriber telephone.
Besides, regarding charging based on the connection between the PSTN and the IP network, another document states a charging system wherein a CA calculates a rental fee involved in an IP network and a connection fee arising between the IP network and an exchange, and an IP business company demands the payment of the fees from an IP telephone owner, while the exchange which accommodates a PSTN subscriber telephone being a called destination calculates the rental fee of the exchange, and the PSTN demands the payment of the rental fee from the IP business company. This technique is stated in, for example, “Nikkei Communications”, Issue of Mar. 3, 2000, p. 89.